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Sucrose-based Polymer: Preparation, Characterization And Its Physiological Effects And Mechanism On Plants

Posted on:2006-11-21Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y Z HeFull Text:PDF
GTID:1100360152994242Subject:Chemical processes
Abstract/Summary:PDF Full Text Request
A New method to synthesize sucrose-based polymer (SBP) was developed and investigated. The use of sucrose in the production of polymers is of growing interest from 1990's, since such polymers demonstrated some attractive and unique properties such as hydrophilicity, biological activity, biodegradability, etc. Conventionally, Sucrose-based polymers were prepared by chemical techniques and enzymatic methods. The new approach, designated as pre-irradiation method and was patented, was found to be a clean, controllable and reliable synthesizing pathway to prepare SBP. Sucrose crystal was pre-irradiated by γ -ray of 60Co and turned into an activated form, then the activated sucrose was polymerizes directly with another monomer (e.g. acrylic acid) to yield SBP, the reaction occurred mildly and cleanly, just in aqueous and room temperature, without any addition of other initiator or chemical.The effects of pre-irradiation dose, reaction temperature, monomer concentration ratio to the relative molecular weight and yield of the polymers were studied. To gain the sucrose-based polymer with 60,000 relative molecular weight which is suitable for agricultural use, the optimal co-polymerization reaction conditions of sucrose with acrylic acid wereestablished as the following: pre-irradiation dose for sucrose, 1kGy; reaction temperature, 20 ℃; reaction time, 15h; monomer concentration ratio, 5:5:1 (water: sucrose: acrylic acid). The preliminary study on reaction mechanism shown the reaction is a radical polymerization. When the samples of sucrose was irradiated with 60Co-gamma radiation under the atmosphere with oxygen, free radicals are generated as stable peroxide that may make the sucrose crystal possessed the activity of initiation (in an activated form). Moved the sucrose away from the radiation field, and simply following regular solution polymerization method in a homogeneous phase system, that is, acrylic acid and the activated sucrose (acted as both the monomer and the initiator) were dissolved in water and reacted for 15 hours, the sucrose-based polymer was obtained. The resulting SBP was separated and further purified, and characterized by 1H NMR, 13C NMR, UV, IR spectra and SEM. The data suggested that it might be a sort of polymer that is different from the previously reported polymers. From the observation by scanning electron microscope, it was found that these polymers consisted of a porous structure. So the SBP is easy to dissolve in water and the thin membrane formed by its solution is proved to possess good ventilative property.More interestingly, the resulting SBP from the pre-irradiation method was found not only the good biodegradable materials, but a novel plant growth regulator (or stimulator) as well.The research of the application of SBP was carried out in several aspects. First, SBP can be used as preservative agent for fruit. Mango, one type of subtropical fruit, was dipped into the solution of SBP and a thin film coated on the surface of Mango. The result showed that the SBP coating film could reduce the respiration intensity of mango and could prevent partially the fruit from microorganism eroding, avoid water evaporating quickly, therefore,prolong the storage life of mango and preserve the original flavor and taste of mango. At normal temperature, the processed mango can be stored 19 days with 80% percentage of good fruits. Secondly, applying SBP as plant growth regulators to the crops, the yields of Pleurotus Ostreatus and maize was increased 20 %, in comparison with the yields of the control. Moreover, SBP was found to be able to raise the soluble solids content and total sugar content, reduce the titratable acidity in the fruits of longan, mango, lanii and malon, and have the function of sweetness enhancement.The investigation in the plant interior responding mechanism to SBP application was also turned out some very interesting results. The experiments data indicated that SBP can increase the chlorophyll content and the rate of photo synthesis of the leaf of the plant, and at the same time decre...
Keywords/Search Tags:sucrose-based polymers, preirradiation method, free radical initiation, structure characterization, fruit preservation, yield rising, plant growth regulator, enzyme
PDF Full Text Request
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